The latest edition of the National Land Cover Database (NLCD 2006) is now publicly available. This massive database updates the extent of our understanding of the nation’s land cover and documents precisely where land cover change has occurred between 2001 and 2006. NLCD is used for thousands of applications ranging from ecosystem status and health, to spatial patterns of biodiversity, indications of climate change, and best practices in land management.
Based on Landsat satellite imagery taken in 2006, the database was constructed in a five-year collaborative effort by the 11-member federal interagency Multi‑Resolution Land Characteristics Consortium (MRLC).
The carefully calibrated data describes the land surface condition of each 30-meter cell of land in the conterminous United States and identifies which ones have changed since the year 2001. Nearly six such cells — each 98 feet long and wide — would fit on a football field. This release of NLCD marks the first time land cover change has been captured for the Nation in such detail, and required several years of new methodological research to accomplish.
The range and accuracy of this information allows researchers with many different interests (for instance, invasive species or hydrogeography) to identify critical characteristics of the land and patterns of land cover change, informing a variety of investigations from monitoring forests to modeling runoff in urban areas.
Land cover is broadly defined as the biophysical pattern of natural vegetation, agriculture, and urban areas. It is shaped by both natural processes and human influences. NLCD 2006 data portrays 16 classes of land cover in the lower 48 states and the degree of surface imperviousness in urban areas. The density of non-transpiring, impervious surfaces — usually composed of concrete, asphalt, stone, and metal — is widely recognized as a key indicator of environmental quality in urban areas.
Official USGS news announcement (from which this blog post was excerpted)